정상 및 Alloxan당뇨병 흰쥐의 뇌절편에 있어서 C14-초성포도당 및 포도당의 대사에 관한 실험적 연구

Abstract

Brain slices of 58 normal and alloxan-diabetic rats were divided into 4 groups. Each group was incubated for a period of 5 hours with incubation mixture consisting of 15 C.c. of phosphate buffer to which were added C1L glucose or C14-pyruvatc and 15 C.c of oxygen. During 5 hours of incubation period. the incubation media and gas phase were replaced with fresh media and oxygen at hourly intervals. This procedure made it possible to obtain hourly samples to determine the concentration of medium substrates and the amount and radioactivity of CO2 produced by the brain slices during the experimental period. It also had the advantage of presenting the tissue with a substrate of essentially constant concentration and specific activity. Data obtained from the C14-pyruvate incubation experiment, in the first and second group , and from the ClL glucose incubation experiment in the third and fourth group , were summarized as the follows. 1. In the ClL pyruvate incubation experiment, pyruvate disappearance rates were mean of 10.7 μM/hr/g in the first control group , and 12. 2 μM/hr/g in the second alloxan-diabetic group. The lactate accumulation rates in both groups were mean of 5. 8 and 5.1 μM/hr/g respectively. Total CO2 production rates in both groups were mean of 49. 7 and 63. 4 μM/hr/g respectively, showing a slightly higher value in the second group. However, since RSA, which represents the fraction of C14-02 derived from medium CILpyruvate to total CO2 production rate, was slightly hiher in the control group than the diabetic-group, there were little diffe• rences in C02 production rates derived from medium CILpyruvate of both groups. 2. In the C14-glucose incubation experiment, ClL glucose disappearance rates decreased about one half of the control in the diabetic group , showing a mean of 44.1 μM/hr/g in the third control group and 20.0 μM/hr/g in the fourth alloxan-diabetic group. Since there were not significant differences in total CO2 production rates and values in RSA, Cl4-0 2 production rates derived from medium clιglucose have been found to be almost the same value in both groups. From the data described above, insulin cannot have an influence on all the steps of carbohydrate metab olism in the brain tissue. However there is evidence that insulin exhibits the effect on membrane transport of glucose as found in the other tissues.